Language structure and language acquisition: grammatical categorization using phonological and distributional information

This thesis addresses the question of how words are grouped according to their grammatical categories during language acquisition. Over the past 20. years a general consensus has developed that distributional and phonological cues are important cues that language learners utilize in the grammatical categorization process (e.g., Kelly, 1992; Redington, Chater, & Finch, 1998). The combination ofthese cues was investigated with artificial language learning experiments, which combined two categories of. phonologically coherent words with co-occurring distributional cues, and corpus analysis techniques. Experiments I to 4 indicated that both phonological and distribution cues are necessary for the categorization of high and low frequency words. Additionally, these experiments indicated that distributional information alone was sufficient to categorize high frequency words, but that phonological cues were necessary for low frequency words. It was also found that succeeding bigram distribution cues induced more grammatical categorization than the preceding bigram cues. This is explained by the Rescorla-'\yagner (1972) model of associative learning; associations were stronger between the category words and succeeding cues as a single succeeding cue followed all category words. Associations were weaker with preceding cues as numerous category words followed the preceding cues. Experiments 5, 6 and 7 also found that the effectiveD~ss of the distributional cues was influenced by prior linguistic experience, resulting in higher learning with distributional cues which were phonologically consistent with distributional cues found in the participants' native language (English). This thesis also investigated the debate as to what type of distributional cue is most useful in the categorization process, with some researchers advocating trigram cues (Mintz, 2002) while others advocate bigram cues (Monaghan & Christiansen, 2004; Valian & Coulson, 1988). The results of a corpus analysis and two experiments provided evidence that trigram cues (aXb) are very effective at categorization, but preliminary evidence suggests that this categorization may simply be due to the combined influence of the beginning and ending bigrams (aX and Xb). Overall, this thesis indicates that phonological and distributional cues are key to grammatical categorization, which occurs through associative learning principles; grammatical categorization progresses .faster with succeeding cues; and bigram distribution cues may be the initial source of distributional information in the grammatical categorization process.